I have been looking at cast signed photos signed at San Diego Comic Con and found interest in some. Many of these posters however, only have the wristband from the signing as their “COA”. Should these wristbands be considered good enough authentication, red flags, or simply not trust worthy?
If they want to throw them in the deal, that's fine. But they really don't authenticate anything. Tons of people went to SDCC.
These wristbands are specifically for that signing. Like a Game Of Thrones autograph signing is stated on one in particular.
Even those don't mean anything.
It just says they had the wristband. It doesn't mean that they actually went to the signing or that the item they got signed is the one they're selling.
So, to answer your original question, none of the above. The wristbands shouldn't be considered anything.
It's like the people who throw book signing fliers in with their signed books. It doesn't mean anything. It certainly doesn't prove anything.
The one thing any of those items are good for is highlighting discrepancies. It doesn't say "this is good", but if someone was lazy in their research, it could say "this is bad".
What I mean by that is let's say that someone signs only their first name at a specific signing, but someone is offering a full name item that they claim was signed there, with the wristband to prove it. Whereas otherwise, it might be up for debate about whether or not it's real, based on all the possibilities and options of when it could've been signed, now you know it's not, since the wristband locks them in to their story.
Same goes for if a signing got cancelled or if the piece is signed by individuals who weren't part of the signing.
I wouldn't ever buy based on the presence of a wristband, but if a forger is stupid enough to try to sell a 1990 signature style with a 2017 SDCC wristband, it'll make it easier to know not to buy vs them just selling what could otherwise be a 1990 signature.